1. Field of the Invention
The present invention relates to the field of computer networking, and, more particularly, to apparatus and methods for allowing two closely coupled heterogeneous computer systems to communicate with each other via a messaging system over an interconnection including a simulated or "virtual" transport layer interface.
2. Description of the Prior Art
The ability for heterogeneous computer systems to communicate with each other over a network using standard ISO and/or proprietary networking protocols is known. Most computer systems have some form of networking architecture that enables the computer system to perform networking in accordance with those protocols. For example, the generic networking platform with the standard 7 layer ISO Reference Model includes a network stack: applications, presentation, and sessions levels under user control, and transport, network, data link, and physical levels under kernel (operating system) control. Typical networking architectures comprise both system software and hardware.
FIG. 1 is a block diagram illustrating the components of a networking architecture employed by a Unisys A Series enterprise server 10 in order to communicate with other hosts, or nodes, on a network 15. The A Series enterprise server 10 executes the Unisys MCP operating system 12, and has an I/O subsystem that comprises one or more I/O Modules (IOM) 14 housed within the A Series chassis. The IOM 14 implements a Unisys proprietary I/O bus architecture referred to as CS-BUS II or CS-Bus III (hereinafter "the CS Bus"). A plurality of card slots, e.g. slots 16a-d, are provided for connecting interface cards, referred to as "channel adapters", into the CS Bus. Different groups, or racks, of channel adapter slots are each controlled by a Channel Manager Unit (CMU) (e.g., CMUs 18a, 18b). An IOM can contain several CMUs, each of which controls a different rack of channel adapter card slots via the CS-Bus. The CMUs manage the physical and data layers of the CS-Bus data transfer protocol.
Channel adapter cards, which each may occupy one or more channel adapter card slots within the IOM 14, provide various connectivity solutions for the A Series enterprise server 10. For example, Unisys provides a channel adapter card that implements the Small Computer System Interface(SCSI) protocol for connecting SCSI peripherals to the enterprise server 10.
For network connectivity, Unisys provides several channel adapters to support various physical networking protocols. These channel adapters are generally referred to as network processors (NP). For example, Unisys ICP22 and ICP26 network processors are channel adapter cards that implement the Ethernet network protocol and can be used to connect an A Series enterprise server 10 to an Ethernet network. Unisys also provides network processors for connectivity to FDDI and ATM networks. As shown in FIG. 1, a number of different network processors (e.g., NPs 20a, 20b, and 20c) can be installed in respective channel adapter slots (e.g., slots 16b, 16c, and 16d) of the IOM 14, in order to provide different network connectivity solutions.
As shown in the more detailed view of network processor 20c (installed in channel adapter slot 16d), a network processor may comprise a plurality of different lines, e.g., Line0, Line1 . . . LineN, where a line represents a physical endpoint within a network. For example, the Unisys ICP22 network processor has two lines, each of which comprises a separate Ethernet connection--one line could be connected to one Ethernet network, and the other to a different Ethernet network.
Each line of a network processor can have one station group defined on that line. A station group consists of one or more stations. A station is a logical endpoint that represents a logical dialog on that line. Thus, more than one logical dialog can take place over a given line of a network processor. This is achieved through multiplexing. For example, with a connection-oriented networking protocol, such as the Burroughs Network Architecture--Version 2 protocol (BNAv2), one station may represent a logical dialog with one other BNAv2 host on the network, whereas another station may represent a logical dialog to a different BNAv2 host. As illustrated in FIG. 1, for example, Station0 of LineN may represent a logical dialog with BNAv2 host 22, and Stationl of LineN may represent a logical dialog with BNAv2 host 24. For networking protocols that are not connection-oriented, like the Internet Protocol (IP), only one station needs to be defined to handle all communications for that protocol stack. For example, in FIG. 1, StationN of LineN could be defined as the logical endpoint for all IP traffic over LineN. A Local Area Network Station Group (LANSG) module 26, which comprises software executing on the network processor 20c, provides callable procedures for creating and maintaining stations and station groups on the various lines of the network processor 20d and for sending and receiving data over them.
Other software components that execute on the network processor 20c include a Queue Service Provider (QSP) module 28, which handles the passing of messages between the NP Support 40 and the channel adapters. QSP module 28 also multiplexes and demultiplexes data for all stations defined on a given NP. Some data is blocked together for efficiency; other data is not. Other components include two stub modules--a Network Services Manager stub (NSM-stub) 30 and a Link Layer Manager stub (LLM-stub) 32--which interface with corresponding modules of a Core Network Services (CNS) software component 34, to and from modules within the MCP environment.
Generally, a network processor (e.g., NP 20a, 20b, or 20c) implements the data link and physical layers of the 7-layer ISO Reference Model. Higher level networking protocols that a client application 46 may wish to employ in order to communicate with applications running on different hosts of the network 15, such as the BNAv2 and TCP/IP networking protocols, are implemented as network protocol providers on the A Series system 10. A network protocol provider is a software module that implements these higher level networking protocols. For example, Unisys provides both BNAv2 Host Resident Network Provider (HRNP) modules and TCP/IP HRNP modules. In the example of FIG. 1, a BNAv2 HRNP 42 and a TCP/IP HRNP 44 are shown.
The Core Network Services (CNS) software 34 provides support for the network protocol providers 42, 44 and handles the initialization and maintenance of network processors and the station groups defined thereon. Specifically, CNS 34 comprises a Network Services Manager (NSM) 36 that initializes and manages the network processors (e.g., 20a, 20b, 20c) installed in the system, and a Link Layer Manager (LLM) 38 that initializes and maintains the identity and attributes of each station group defined on a given network processor. Another component (not shown) of CNS 34 validates attributes associated with station groups and stations created on a network processor. These attributes are passed between the network processor and CNS 34 via a control dialog when the stations are defined. Like the stub procedures for the NSM and LLM modules 36, 38, network processors also have a stub procedure (LLAH, not shown) that corresponds to the attribute handler of CNS 34. An NPSUPPORT software library 40, as well as portions of the MCP operating system 12, provide routines and procedure calls that serve as an interface between a network processor and the CNS 34 and network protocol providers 42, 44, and control loading of software to the NPs and dumping of their state.
Each network processor has an associated identifier that uniquely identifies that network processor within the system 10. When a network processor is initialized and brought on-line, the NSM-stub 30 in the network processor interfaces with the NSM 36 of CNS 34 via a control dialog in order to pass its identifier to the NSM 36. The NSM 36 manages the identifiers of all active network processors.
Each station group and station defined for a given network processor also has a unique identifier associated with it. Via a control dialog established between the LLM-stub 32 on the network processor and the LLM 38 of CNS 34, the station and station group identifiers are passed to the LLM 38 during initialization. Within the LLM 38, a station corresponds to a connection, and a station group corresponds to a connection group.
As mentioned above, the ability to define multiple stations (i.e., a station group) on a single physical line of a network processor is achieved through multiplexing. Specifically, the QSP 28 in the network processor multiplexes inbound and outbound data for multiple stations on a given line. Moreover, the QSP 28 is responsible for distributing request and response data between the NSM 36 and NSM-stub 30 and between the LLM 38 and LLM-stub 32. To that end, each entity on the network processor that receives outbound data from the MCP 12, including every station, the NSM-stub 30, and the LLM-stub 32, is assigned a unique Remote Queue Reference (RQR) by the QSP 28. The NSM-stub RQR is reported to the NSM 36 within CNS 34 via NPSUPPORT 40 when the NP is loaded. The LLM-stub RQR is reported to the LLM 38 via the NSM 36 by the NSM-stub 30 when the network processor initializes. All of the station RQRs are reported to the HRNPs 42, 44 as the stations open.
When a client application is required to send data via network 15 to some other host or node on the network 15, such as another BNAv2 Host 22, 24 or another TCP/IP host 25, it invokes the services of the appropriate network protocol provider, e.g., 42, 44. The network protocol provider 42, 44 determines the appropriate network processor and station on which the data is to be output, adds protocol headers for each of the network layers, and makes a corresponding request to the MCP 12 that includes the identifier of the network processor and the RQR of the station. The data and associated RQR are passed from the MCP 12 to the QSP 28 on the network processor (e.g., network processor 20c), which, in combination with the LANSG module 26, sends the data out to the network 15 via the appropriate line (e.g., Line0, Line1, . . . or LineN) as part of the logical dialog represented by the designated station.
When data is received from the network 15 on a given line, the LANSG module 26 determines, from header information associated with the data, the station (i.e. logical dialog) for which the data is intended. The LANSG and QSP modules 26, 28, in combination with portions of the MCP 12 and NPSUPPORT library 40, pass the received data to the appropriate network protocol provider 42, 44 associated with that station, along with an indication of which station received the data. For example, one of the stations on LineN of the network processor 20c of FIG. 1 (e.g., station0) may be defined as the logical endpoint for the BNAv2 HRNP 42, while a different station (e.g., station1) may be defined as the logical endpoint on which all IP traffic over LineN is received for the TCP/IP HRNP 44. When a frame of data is received from the network on LineN, the LANSG module 26 determines from header information which of the network protocol providers (i.e., stations) is intended to receive the data. This determination is performed in accordance with the methods described in commonly assigned, U.S. Pat. No. 5,379,296, entitled "Method and Apparatus for Interfacing a Workstation to a Plurality of Computer Platforms" (Johnson et al.).
In addition to its use in A Series computers, the foregoing networking architecture is also employed in Unisys ClearPath HMP NX enterprise servers. A ClearPath HMP NX server comprises an A Series enterprise server tightly integrated with a server running Microsoft Window NT. Please note that "Microsoft," "Windows," and "Windows NT" are registered trademarks of Microsoft Corporation. Additional information concerning the foregoing networking architecture can be found in the following documents, each of which is available from Unisys Corporation, assignee of the present invention, and each of which is hereby incorporated by reference in its entirety:
ClearPath HMP NX Series with Windows NT Network Services Implementation Guide (Part No. 4198 6670); BNA/CNS Network Implementation Guide, Volume 2: Configuration (Part No. 3789 7014);
ClearPath HMP NX Series with Windows NT Implementations and Operations Guide (Part No. 8807 6542);
ClearPath HMP NX Series with Windows NT Migration Guide (Part No. 8807 7730);
Networking Capabilities Overview (Part No. 3789 7139);
Networking Operations Reference Manual, Volumes 1 and 2: Commands and Inquiries (Part No. 3787 7917); and
Networking Products Installation Guide (Part No. 4198 4840).
Using a Unisys ICP22 network processor, which is an Ethernet-based channel adapter, it has been possible in the past for a Unisys A Series enterprise server to communicate with a workstation or personal computer (PC) over a network. An example of this ability is illustrated in FIG. 2. In this example, the A Series enterprise server 10 communicates with an Intel-based workstation 48 running the Microsoft Windows NT operating system (hereinafter "the NT server"). The A Series enterprise server 10 is connected to the network via network processor 20a, which may, for example, be a Unisys ICP22 Ethernet-based network processor.
The I/O subsystem of the NT server 48 comprises portions of the NT operating system kernel, an EISA or PCI bus 52, and appropriate device driver software. To provide network connectivity, a network interface card (NIC) 50 is installed in an available bus slot on the NT server 48. The NT server may support one or both of the PCI and EISA bus standards. NICs are available for both bus standards.
A NIC device driver 54 that typically is sold with the NIC card 50 is installed in the kernel space of the NT operating system. The NIC device driver 54 interfaces with a higher level network protocol provider, such as an implementation of the transport (TCP) and network and data link (IP) protocols. Microsoft Corporation provides an implementation of the TCP/IP protocol in the form of a kernel level device driver, also referred to as a transport protocol driver, named TCPIP.SYS 58. TCPIP.SYS 58 interfaces with the NIC device driver 54 via NDIS 56, an industry standard Network Driver Interface Specification jointly developed by Microsoft and 3Com. NDIS 56 defines an interface for communication between hardware-independent protocol drivers, such as TCPIP.SYS 58, which implement the Data Link, Network, and Transport layers of the ISO model, and hardware-dependent NIC drivers 54 which provide an interface to the NIC hardware and which correspond to the Physical Layer of the ISO model. A client program 60 on the NT server can communicate over the network 15 in accordance with the TCP/IP protocol by issuing suitable calls via the NT operating system to the TCPIP.SYS protocol driver 58, and the A series server 10 and NT server 48 communicate over network 15 at the physical layer of the ISO model.
To avoid the costs associated with the development of NIC cards for proprietary systems such as the A series enterprise server, it has been proposed in co-pending U.S. patent application Ser. No. 09/088,421, also assigned to the present assignee and the contents of which are hereby incorporated by reference in their entirety, to provide a direct interconnection between A series enterprise server 10 and NT server 48 so that both systems may connect to a network via a shared network interface card installed on the NT server. Such an invention is implemented as part of a Cooperative Networking Platform (CNP) deployed on a Unisys ClearPath HMP NX computer system ("the ClearPath system"). As will now be described, the ClearPath system comprises a Unisys A Series enterprise server 100 and an Intel-based server 102 running Windows NT 102 ("the NT server").
As shown in FIGS. 3, 4, and 5, the CNP may take different forms. As illustrated in these figures, the interconnection couples the I/O subsystem of the A Series server 100 to the I/O subsystem of the NT server 102 to provide a relatively high speed data path between systems. Preferably, the interconnection comprises a physical connection between the I/O subsystems of the A series enterprise server 100 and the NT server 102 and an interconnection device driver that controls access to the physical connection by other software modules on the NT server 102.
In the embodiment of FIG. 3, the physical connection comprises a feedthrough card 62 installed in a channel adapter slot of the A Series server 100, an EISA Personal Computer Channel Adapter (EPCCA) card 66 installed in an EISA slot of the I/O bus of the NT server 102, and a CS-BUS II cable 64 that connects the CS-BUS II of the A Series server 100 to the EPCCA card 66 via the feedthrough card 62. The interconnection device driver (ICD) 70 is installed in the kernel space of the NT operating system and controls access to the physical connection (specifically the EPCCA card 66) by other modules on the NT server 102. The prior art embodiment of FIG. 3 also includes a Queue Service Provider module 76 that functions analogously to the QSP 28 of FIG. 1, a LANSG module 78 that functions analogously to the LANSG module 26 of FIG. 1, and NSM-stub and LLM stub modules 84, 86 of CNP.EXE 80 that function analogously to the corresponding components 30, 32 of FIG. 1. In addition, LDM and LLAH modules 82, 88 of CNP.EXE 80 are provided which function analogously to the similar components (not shown in FIG. 1) in a traditional Unisys networking architecture.
In FIG. 3, the interconnection device driver 70, including its PCCA and OPENCA drivers 72, 74, and the physical connection formed by the feedthrough card 62, cable 64, and EPCCA card 66, together define a Host Interface Function (HIF). The procedural interface between the QSP 76 and the interconnection device driver 70 of the HIF is designed to isolate the QSP 76 from the HIF. As will be apparent from the detailed description below, this enables the present invention to be employed with different implementations of the HIF. Specifically, the procedural interface between the QSP 76 and the interconnection device driver 70 is established through a process by which each module publishes entry points (i.e., pointers) to the procedures that implement its functionality, along with any required variable values. Another device driver entity maintains a record of these entry points, while the interconnection device driver 70 of the HIF registers the entry points and their attributes and the QSP 76 registers the entry points.
In order to invoke one of the entry point functions, a call is made to the registered entry point for that function. As a result of this indirection, different interconnection device drivers are installed for different implementations of the HIF in a manner that is completely transparent to the QSP 76.
FIGS. 4 and 5 illustrate two alternate embodiments of the HIF, which illustrate the modularity provided by the procedural interface design. In FIG. 4, the physical connection (i.e., the feedthrough card 62, cable 64, and EPCCA card 66) is replaced by a PCI Bridge card 67 that connects via a cable 65 directly to a port on one of the CMUs 18b of the IOM 14 of the A Series server 100. By connecting directly to the CMU 18b, some of the latency inherent in the CS-Bus II protocol is avoided. This provides a more direct, higher speed connection between the I/O subsystems of the two servers 100, 102. Because the physical connection is changed, a modified interconnection device driver 70' is provided. The modified interconnection device driver 70' comprises a single device driver module, PXN 73, that provides the interface between the QSP 76 and the hardware on the PCI Bridge card 67. However, the procedural interface, and the mechanism by which the QSP 76 and interconnection device driver 70' register entry points to the respective procedures of that interface is unchanged. Accordingly, the changes to the HIF are transparent to the QSP 76 and the other modules that comprise the Cooperative Networking Platform (CNP).
FIG. 5 is an embodiment in which the A Series server 100 is emulated through software in the NT server 102. Unisys provides such an emulated system in its ClearPath HMP NX 4200 series enterprise servers. In this embodiment, the physical connection is emulated such that it becomes a memory-to-memory connection 63 between the memory space of the emulated I/O subsystem 14' and the memory space of the NT system 102. The emulated connection 63 functions in a manner similar to the feedthrough card 62, cable 64, EPCCA card 66, and PCCA 72 components of the hardware implementation of FIG. 3. The interconnection device driver 70' in this embodiment comprises a modified form 74' of the OPENCA module 74 of the implementation of FIG. 3. Again, however, the procedural interface between the modified OPENCA module 74' and the QSP 76 is not changed, so that the emulated A Series server 100 and its emulated connection 63 to the NT server 102 is transparent to the QSP 76 and the other modules of the present invention that comprise the Cooperative Networking Platform (CNP).
Also, a "virtual" LAN device driver 79 and an NDIS Miniport Interface Library 81 together with LANSG and the remainder of the interconnection components in the systems of FIGS. 3-5 provide a high speed, low latency communications path between the A Series server 100 and the NT server 102 as described in co-pending U.S. patent application Ser. No. 09/088,552, also assigned to the present assignee and the contents of which are hereby incorporated by reference in their entirety. As described therein, these modules, in combination with the physical connection (e.g., feedthrough card 62, cable 64, EPCCA card 66 and the interconnection device driver 70), simulate a traditional channel adapter-based network processor of the type described above and illustrated in FIG. 1. VLAN 79 allows the A series enterprise server 100 and the NT server 102 to both use their native mechanisms to communicate with each other rather than conventional network communications paths such as Ethernet, which may be considerably slower. In particular, VLAN 79 allows the A series enterprise server 100 and the NT server 102 to communicate at the data link level of the ISO network reference model by simulating the physical level with the HIF.
It is desired to further improve the communications efficiency of the ClearPath system by simulating the TCP transport protocol and the IP networking protocol between the A series enterprise server 100 and the NT server 102 via the interconnect so that data may be transferred point to point between systems at the transport level rather than the data link level. By simulating the transport and network layer protocols, it is also desired to remove the inherent limitations of the TCP/IP protocols by using a more reliable network connection through which larger blocks of data may be transmitted without being broken up into smaller data chunks with prepended network protocol information. Of course, it is desirable that this be accomplished in a manner which is transparent to the user (i.e., the session level is unaffected). The present invention provides such capabilities.